Thin film diodes are in widespread use, and in general, thin film manufacturing techniques are less expensive and produce higher yields than wafer scale processing techniques used to fabricate crystalline or “discrete” diodes. Nevertheless, known thin film diodes have characteristics which are poorly suited for many applications.
For example, the rigid substrates on which thin film diodes are fabricated prohibits their use in applications in which the device must be physically deformed. Further, contaminants from metallic contact layers frequently react with the semiconductor body during processing, and thereby degrades the diode's electrical characteristics. Since the diodes are typically used with other semiconductor devices, the diodes must be separately fabricated and interconnected.
U.S. Pat. No. 5,155,565 discloses an amorphous silicon thin film p-i-n solar cell and Schottky barrier diode on a common substrate, comprising:
a substrate;
a first conductive layer on the substrate;
an unseparated amorphous silicon ohmic contact layer over a solar cell portion and a diode portion on the first conductive layer;
one or more layers of amorphous silicon forming a diode body over the diode portion on the ohmic contact layer, including a layer of n-type silicon doped to a concentration of 1018 to 1020 atoms per cubic centimeter with an element from Group V on the periodic table;
at least two layers of amorphous silicon forming a p-i-n solar cell body in conjunction with the ohmic contact layer over the solar cell portion on the ohmic contact layer, adjacent to and spaced from the diode body to form a separation between the solar cell body and the diode body;
insulating material within the separation between the diode body and solar cell body, the diode body and solar cell body electrically interconnected by the first conductive and ohmic contact layers; and
a second conductive layer on the diode body and on the solar cell body, the diode body forming a Schottky barrier with the second conductive layer.
A high density, optically corrected, micro-channel cooled, V-groove monolithic laser diode array is disclosed in U.S. Pat. No. 5,828,683. The laser diode array comprises:
a substrate having an upper surface and a lower surface;
a plurality of v-grooves formed in the upper surface; a metalization layer formed on the upper surface and within the plurality of v-grooves;
a metalization break formed in each v-groove of the plurality of v-grooves; and
a plurality of laser diode bars, wherein a single laser diode bar of the plurality of laser diode bars is placed within each v-groove of the plurality of v-grooves.
U.S. Pat. No. 6,229,153 B1 discloses a high peek current density resonant tunneling diode comprising:
a) a substrate of nominally exact (100)+/−0.5° GaAs;
b) a multilayer resonant tunneling diode structure grown on the (100) GaAs substrate, the resonant tunneling diode structure comprising a quantum well layer of low band-gap material between barrier layers of AlGaAs, and wherein the material of the quantum well layer is selected such that the second energy level of the quantum well layer is at or slightly above the conduction band edge in GaAs, the quantum well layer grown to be a strained layer with smooth interfaces with the barrier layers.
R. A. Gibson et al., in RECENT DEVELOPMENTS IN AMORPOHOUS SILICON p-n junction devices, Journal Of Non-Crystalline Solids, 35 & 36 (1900) 725-730 North-Holland Publishing Company, disclose amorphous Si p-n junctions with various doping profiles prepared by the glow discharge process to investigate the effect of the barrier profile on the electrical properties of the diodes. The highest current densities, up to 40 A/cm2, is obtained with n+-i-p+ structures. Under AM-1 illumination, photovoltaic p+-i-n30  cells generate open circuit voltages of 0.7V and short-circuit currents up to 10 mA/cm2, corresponding to efficiencies between 3 and 4%. Diode quality factors are also investigated.
There is a need for a thin film diode that tolerates a high forward current density and is capable of many potential applications in consumer electronics, such as memory devices, photo-imaging detectors, and flat panel displays. The development of a simple and inexpensive ultra-high-current density thin-film Si diode would have a great impact for replacing the complicated and expensive thin film transistors that currently dominate all thin film consumer devices, and for significantly increasing the density of the elements or pixels in these consumer devices.